The Bacterial Cell – Key Vocabulary

A comprehensive set of vocabulary flashcards covering bacterial structure, genetics, physiology, and classification as presented in the lecture notes.

Cell Theory

The principle that all living things are made of cells and all cells arise from pre-existing cells.

Prokaryotic Cell

A cell lacking a membrane-bound nucleus and membrane-bound organelles; includes bacteria and archaea.

Eukaryotic Cell

A cell that possesses a membrane-bound nucleus and numerous membrane-bound organelles.

Nucleoid

Non-membranous region in a prokaryote where the single circular chromosome is aggregated.

Plasmid

Small, circular, extra-chromosomal DNA molecule in bacteria that carries non-essential but often advantageous genes.

Genetic Recombination

Exchange of genetic material that creates new gene combinations on a chromosome.

Vertical Gene Transfer

Transmission of genes from parent to daughter cells during binary fission.

Horizontal Gene Transfer

Movement of genes between existing bacterial cells; includes transformation, conjugation, and transduction.

Transformation

Uptake of free DNA from the environment by a competent bacterial cell.

Conjugation

Plasmid-mediated DNA transfer between bacteria through a pilus.

Transduction

Transfer of bacterial DNA from one cell to another via a bacteriophage (virus).

Competent Cell

A bacterial cell capable of taking up DNA from its surroundings during transformation.

Antibiotic Resistance Gene

A gene that enables a bacterium to survive exposure to a specific antibiotic.

R (Resistance) Factor

Plasmid containing antibiotic resistance genes transferred during conjugation.

Virulence Gene

A gene whose product enhances a bacterium’s ability to cause disease.

Coccus (plural Cocci)

Spherical bacterial cell shape.

Bacillus (plural Bacilli)

Rod-shaped bacterial cell.

Coccobacillus

Short, oval rod intermediate between cocci and bacilli.

Vibrio

Slightly curved rod-shaped bacterium.

Spirillum (plural Spirilla)

Rigid, helical (corkscrew) bacterial shape often with external flagella.

Spirochete

Flexible spiral bacterium with internal flagella (axial filaments).

Glycocalyx

Viscous polysaccharide-protein layer external to the cell wall; includes slime layers and capsules.

Slime Layer

Unorganized, loosely attached glycocalyx easily washed away.

Capsule

Highly organized, firmly attached glycocalyx that protects against phagocytosis.

Biofilm

Community of microorganisms attached to a surface and embedded in a self-produced matrix.

Peptidoglycan

Rigid polymer of sugars and amino acids forming the bacterial cell wall’s structural backbone.

Cell Wall

Semi-rigid structure outside the plasma membrane that maintains shape and prevents osmotic lysis.

Gram-Positive Bacterium

Bacterium with thick peptidoglycan, teichoic acids, and a purple Gram stain result.

Gram-Negative Bacterium

Bacterium with thin peptidoglycan, outer membrane, periplasmic space, porins, and a pink Gram stain result.

Teichoic Acids

Polymers in Gram-positive cell walls that reinforce structure and aid adherence.

Outer Membrane

Lipid bilayer external to peptidoglycan in Gram-negative bacteria containing lipopolysaccharide and porins.

Periplasmic Space

Region between the plasma membrane and outer membrane of Gram-negative bacteria.

Porin

Protein channel in the outer membrane of Gram-negative bacteria allowing passage of small molecules.

Plasma (Cell) Membrane

Phospholipid bilayer with proteins that acts as a selectively permeable barrier.

Cytoplasm

Gelatinous 70-80 % water solution of salts, sugars, and amino acids inside the cell.

Ribosome (70S)

Prokaryotic particle of rRNA and protein that synthesizes proteins.

Inclusion/Granule

Non-membranous reserve deposit storing nutrients such as glycogen or gas vesicles.

Thylakoid (in Cyanobacteria)

Plasma-membrane infolding containing chlorophyll for photosynthesis.

Endospore

Dormant, highly resistant bacterial cell formed during sporulation under harsh conditions.

Sporulation

Process by which a vegetative cell forms an endospore.

Germination

Return of a dormant endospore to metabolically active vegetative growth.

Flagellum

Long helical filament used for bacterial motility; rotates 360°.

Basal Body

Rod-and-ring structure anchoring the flagellum to the cell wall and membrane.

Filament (Flagellar)

External helical portion of a flagellum composed of flagellin protein.

Run

Straight swimming period when flagellum rotates counterclockwise.

Tumble

Brief reorientation when flagellum rotates clockwise before the next run.

Taxis

Directed movement toward or away from a stimulus (e.g., chemotaxis, phototaxis, thermotaxis).

Chemotaxis

Movement of bacteria in response to chemical gradients.

Phototaxis

Movement of bacteria toward or away from light.

Thermotaxis

Movement of bacteria in response to temperature changes.

Fimbria (plural Fimbriae)

Short, bristle-like protein appendage for adherence to surfaces or other cells.

Pilus (plural Pili)

Long, rigid protein tube used primarily for conjugation and DNA transfer.